At present, cellular phones require much more various parts to pursue multifunctionality while following a trend toward compactness and lightweightness. Thus, a SIM card for identification of a subscriber also continues to follow a trend toward compactness.
Conventionally, an original SIM card (see FIG. 1(a)) used to identify subscribers of cellular phones is of the order of 25 mm and 15 mm in length and width, respectively, and a micro SIM card (see FIG. 1(b)) that has been used so far since the original SIM card was released is of the order of 15 mm and 12 mm in length and width, respectively. Currently, a nano SIM card (see FIG. 1(c)) 12 mm and 8 mm in length and width that are smaller than those of the micro SIM card began to be applied to real products.
The SIM card employs six connection parts 11 to 16 in a GSM scheme, but further employs two connection parts 17 and 18 for use in a transportation card in Korea. Resultantly, a total of eight connection parts are often used in the SIM card.
Typically, a socket configured to be installed in cellular phones so as to mount the SIM car has a structure that is disclosed in Korean Patent Registration No. 1201667 as shown in FIG. 2.
The socket includes: a housing 100 made of a synthetic resin material, a plurality of terminals 200 each having a contact part 210 mounted on the housing 100 and brought into close contact with an associated one of connection parts of an SIM card 10 and a soldering part 220 configured to be soldered to a printed circuit board; a cam slider 300 including a slider 310 having a heart cam 311, a spring 320, and an operating rod 330, and configured to insert and withdraw the SIM card 10 into and from the socket; and a cover 400 made of a metal material and coupled to the top of the housing 100 to define a space between the housing 100 and the cover 400 so that the SIM card is inserted into the space.
The terminals of such a conventional socket are configured such that the soldering parts are arranged in a row at a rear side of the socket and the contact parts have support points at a front side of the socket. The contact parts are formed in a cantilever shape which is extended toward the rear side of the socket. The contact parts of the terminals are exposed to the outside through through-openings for use in installation of the terminals on the housing so that they are brought into close contact with the connection parts of the SIM card by the elasticity of the cantilevers.
In case of the conventional SIM card shown in FIGS. 1(a) and 1(b), the connection parts are arranged in two rows. However, in case of the terminals of the socket connected to the connection parts of the SIM card, the soldering parts are arranged in one row, and thus there occur many cases where it is difficult to grasp the arrangement structure of the soldering parts of the terminals upon the design or after the assembly of the socket. In particular, the soldering parts are arranged in one row, and thus the soldering parts are densely spaced. In addition, since the soldering parts are protruded to the outside of the housing, various electrical failures occurs due to foreign substances introduced between the soldering parts of the respective terminals during the soldering of the soldering parts
Particularly, in case of the smallest nano SIM card among the existing SIM cards, the spacings between the connection parts are the same as those of the conventional SIM card, but the entire size of the nano SIM is small and thus the size of the socket is small, making it difficult to sufficiently secure the spacings between the soldering parts. As a result, it is difficult to identify the arrangement structure of the soldering parts, which further greatly influences the introduction of foreign substances between the soldering parts.
In addition, in a structure of the socket shown in FIG. 2, a part of the SIM card is required to be protruded to the outside of the socket in order to fixedly insert and withdraw the SIM card into and from the socket in a push-push pattern by the operation of a heart cam. Also, the lengths of the cantilevers constituting the contact parts of the respective terminals are required to be equal to each other so that a contact force applied to the terminals are substantially constant. However, the nano SIM card as shown in FIG. 1(c) entails a problem in that the spacing L between the connection parts and the outer peripheral edge of the nano SIM card is small, making it difficult to sufficiently secure the length of the cantilevers constituting the contact parts of the respective terminals of the socket. In addition, the nano SIM card encounters another problem in that when the length of the cantilevers is made large, the size of the socket is increased, and thus the nano SIM card is concealingly inserted inside the socket, making it difficult to externally perform the push-push operation.